A. Field of Invention
The present invention relates to pipe tongs or power tongs used in the oil and gas industry to make-up and break-out sections of drill pipe and other tubular members having threaded connections. More particularly, the present invention relates to a jaw for use in such tongs and a method for constructing the jaw.
B. Description of Related Art
Power tongs are often employed in the oil and gas industry to break-out or make-up threaded connections on tubular members (such as drill pipe, tubing, or casing). It is generally required that one tong grip and rotate one section of a tubular string and a second tong grip and hold stationary the other section of the tubular string. The first tong rotating the first tubular member is typically referred to as the power tong, while the second tong holding the second tubular member stationary is typically referred to as the back-up tong. Examples of conventional power tongs can be seen in references such as U.S. Pat. Nos. 5,671,961, 5,702,139, and 5,819,604 to Buck, which are incorporated herein by reference.
Power tongs ordinarily have two or more jaws which are actuated to grip and release the tubular member. The actual contact with the tubular is typically accomplished through the use of die inserts which are removably positioned in the power tong jaws. Die inserts are commonly held in place through a dovetail key arrangement or other groove and spline configurations as seen in U.S. Pat. No. 4,576,067 to Buck, which is incorporated herein by reference, and the patents cited therein.
Power tong jaws are commonly machined from solid pieces of metal bar stock, or semi-finished casting or from ring forgings which are rolled to near final dimensions and then machined to final dimensions. An example of jaws 1 constructed in this manner is seen in FIG. 1. It can be seen that the jaw 1 includes a jaw body 4 with dovetail slots 3 formed therein. The rear portion of the jaw body 4 includes a jaw roller 5 secured to the jaw body 4 by a roller pin 6. A number of machine hours on lathes, mills, and saws are required to construct these jaws 1 from the preliminary material. A portion of these hours are spent forming the complex dovetail slot 3 in the jaw 1, which dovetail slot 3 receives the die insert 2. The process of forming jaws from solid material in this manner is costly and time consuming.
Jaws are often formed from multiple pieces for applications where the weight of a completely solid jaw might be excessive. An example of such jaws 106 is seen in FIG. 2. Lower and upper plates 100 and 102 are cut, e.g., using a laser, waterjet, or torch. Afterward, the plates 100 and 102 must be machined or milled before they are connected to a jaw mid-section 101 using bolts 105. Like the solid jaws 1 discussed above, the jaw mid-section 101 is cut from metal bar stock or ring forging and machined. Although the jaw mid-section 101 is smaller in diameter than the solid jaw 1 (and, therefore, involves less material), like the solid jaw 1, the jaw mid-section 101 contains dovetail slots 104 for receiving die inserts 103. As noted above, substantial machine work is required to form these dovetail slots 104. Thus, the process of constructing jaws in this manner is less expensive than constructing jaws out of solid material, but this manner of constructing jaws is still costly—primarily because of the machine work that must be done on the jaw mid-section 101, especially the complex machine work required to form the dovetail slots 104. What is needed in the art is a power tong jaw design which may be manufactured less expensively, from less preliminary material, and requires less machine work.